1. Field of the Invention
The invention proceeds from an iron aluminide coating and provides a method of applying an iron aluminide coating to a substrate.
2. Background
EP 0 625 585 B1 has disclosed a Fexe2x80x94Crxe2x80x94Al alloy possessing high oxidation resistance. Said alloy has been used to produce foils for catalyst supports in catalytic converters.
Coatings produced from this alloy, however, especially at high temperatures and as a coating of thermally stressed elements of thermal turbomachines, exhibited inadequate oxidation properties.
In order to apply heat insulation coats to blades, heat shields, etc. of thermal turbomachines and combustion chambers, it is common to apply to these elements a bonding layer by the vacuum plasma technique. Disadvantages of these bonding layers are that the bonding layer commonly fails at service temperatures above 900xc2x0 C., and the heat insulation coat falls off, and also the inadequate oxidation resistance of the bonding layer.
Accordingly, one object of the invention is to improve the oxidation behavior of an iron aluminide coating of the type referred to at the outset.
This object is achieved in accordance with the invention by providing an iron aluminide coating having the following composition:
the remainder being iron and also impurities and additaments arising from its production.
One of the advantages of the invention is that the coating has good oxidation resistance, especially at temperatures above 1000xc2x0 C. The use of intermetallic phases, moreover, has the advantage that the coating does not fail even at high temperatures; this is a particular advantage if the coating is used as a bonding layer for a heat insulation coat. The iron aluminide coating is therefore of outstanding suitability as a coating and bonding layer for thermally stressed elements of thermal turbomachines.
The ductile brittle transition temperature (DBTT) of the coatings of the invention is situated lower than that of conventional nickel-based coatings, which is highly advantageous for their use as coatings.